The present invention relates to aerological condition measurement methods and apparatus. More particularly, the present invention is directed to methods and apparatus for continuously monitoring wind conditions such as wind velocity and wind direction at various altitudes and indicating these through visual mechanisms.
Currently, the most scientific way to measure wind velocity is to build a tower, instrument it with anemometers and record. Anemometers measure wind velocities in many different ways. The common spinning cups turn an electric generator. Resistance change with the heat dissipation from a hot-wire anemometer is used to measure the wind velocity. The anemometers must be put into the actual wind so that the velocity may be determined. Many of these towers have been built. Unfortunately, if it is desired to measure wind velocity at another site or altitude, or study flow patterns, a further tower has to be built or the first tower has to be moved. This process is extremely expensive and impractical for many reasons.
The prior art has attempted to determine wind velocity and wind direction through the use of aerostatic devices such as balloons. The French Pat. No. 971,300 discloses a device for aerological soundings. The aerostatic device lifts as a function of the material with which it is inflated. The balloon is tethered to one end of a line that is wound around a drum at the other end thereof. The patentee states that a tractive effort is determined through the use of a dynamometer. While the patentee states that a wind velocity is determinable, no such method of determining this wind velocity is disclosed therein. The tractive effort is said to be due to the upward force of the balloon and, additionally, the wind velocity. The patentee does not disclose how the amount of tractive effort due to the wind velocity is distinguished from the aerostatic lifting force. Furthermore, it has now been found that a balloon acting under aerostatic conditions cannot be operated in wind speeds beyond 20 knots. Such an aerostatic vehicle is completely unstable under high velocity wind conditions. That is, the winds will blow it downwardly and create an impossible situation for measuring wind velocity.
The ballon or aerostatic device has expanding characteristics which are unknown under changing conditions of temperature pressure and air density. The drag on the ballon is proportional to the cube of the area which varies both with altitude and temperature. Thus, it is impossible to calibrate an aerostatic device in conjunction with the line tension determined on the tether line. This new fact as reported in an article published in the Bulletin of the American Meterological Society, Volume 56, No. 9, at page 964, expressly contradicts the teaching of the French patent noted above. At a certain altitude, the aerostatic device or balloon will collapse when it bursts from its internal pressure exceeding the atmospheric pressure which changes with respect to altitude.
The conventional wind sock is used virtually all over the world at airports for the purpose of giving a visual indication of wind direction and velocity. The conventional wind sock has an opening through which the wind blows and expands the sock by an amount depending upon the type of material being used and the size of the wind sock. These materials and sizes provide the disadvantage of not being very sensitive in their response to wind condition changes. The size of the mast and sock itself make it virtually impossible to be placed near the runway where the landing or takeoff is to occur. Very often, the wind condition near the wind sock installation is quite different from that existing near the actual point of takeoff or landing for the aircraft on the runway. The wind sock is not sensitive enough to determine wind change characteristics in operations where there are turbulence producing obstructions and buildings such as in a heliport area.